This invention relates to a mobile or stationary cleaning and treating unit, and more particularly to an apparatus for high pressure spray application in the cleaning and treating of large structures, such as mobile homes, trucks, automobiles, buildings, and the like. Through a novel control system and a self-contained heating system, different cleaning and treating sprays may be employed.
Mobile units for on-site cleaning and treating operations are shown in U.S. Pat. Nos. 3,567,342; 4,213,796; and 4,290,442, which are herein incorporated by reference. The units described therein are compact and self-contained, each carrying its own water (optional), cleaning and treating compounds, and the like, as well as power generating equipment to produce a high pressure spray.
Cleaning with units of the type of this invention is more efficient than those using low water pressure. In particular, the use of high pressure positive displacement pumps and correct proportions of various treating agents with water provides better and more efficient cleaning. A relatively compact mobile van may house and carry the washing equipment, which is fixed within the van except for one or more spray hoses with remote applicators and control valves.
The pumps that provide the high pressure spray in the cited prior art patents are driven by electricity from generators driven by a power unit in the truck. Water in an internal storage tank is maintained at its initial temperature (not heated to a higher temperature) through the use of an electric heating element. Unloader valves are provided with the positive displacement pumps to permit operation of the pumps while the spray outlet is turned off. Provision has been made for mixing various liquid cleaners with water drawn from the storage tank carried by the truck and supplied to the hose and applicator by the pumps.
In the units disclosed in the latter two aforementioned patents, an improvement was incorporated comprising selection from a series of cleaners to be added to the water by sensing the change in fluid flow caused by opening and closing a flow valve on the applicator. Tanks were provided for the different cleaning additives and a selector valve assembly selected the desired additive. Operation of the selector valve was triggered by a change in the fluid flow through the applicator sensed by a flow switch in the supply line to the pump. The selector valve assembly sequentially advantaged to the near additive tank in a preselected sequence in response to each closing of the applicator flow valve. This method had the advantage of the needing no electrical switches or other remote control external to the van, other than the applicator's on and off valve. This allowed the operator to control the choice of additives while applying the solutions. There was no need for the operator to return to the unit itself or to run wires and switches to the operator's position, or to use more sophisticated devices, such as radio remote control.
Unfortunately, while these advantages were achieved there was a disadvantage. The sensing of fluid flow was not usable with the entire range of fluid application rates necessary to handle different cleaning situations. In particular, a range of 2-5 gal./min. was proven to be too broad for reliable switching of the different cleaning additives.
A further problem with the units described in the aforementioned patents is that they were only suited to apply liquids at their initial temperature. Electrically heating the contents of the water storage tank beyond that necessary to maintain an initial temperature was not practical without external electrical power. In addition, the previous units employed an electrical generator system to provide power for the pumps and other accessories. This required not only a generator, but also electrical motors. Both the power available and the efficiency achievable are limited. In addition, 110 volt a.c. or higher voltage required more care, when used with a mobile unit in a wet environment, than low-voltage 12 volt direct current that is normally available in a vehicle.